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PSYC 1010 Study Guide - Standard Deviation, Statistical Hypothesis Testing, Test Statistic

Course Code
PSYC 1010
Harvey Marmurek

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Chapter 7
Raw Scores, z Scores, and Percentages
Step 1: convert raw score to z score
Step 2: look up area in Table B1
when you look up a number in the table in the % part it tells you the *area between mean and z*
-the table presents area between the mean and z and beyond the mean and z
To convert to a Raw Score
-if the population mean is 500 and the standard deviation is 100 and the z is 0.33 (or 63rd % tile)
x=z(SD) + population mean
x= 0.33 (100) + 500
= 33+500 =533
Z Table and Means
-need to calculate standard error because variability is smaller for distribution of means than for
distribution of scores
A sample with N=36 has a mean = 533 from a population with a mean = 500 and standard
deviation = 100
whats the z score?
-standard error = 100/6 (square root of N) = 16.67
-z = (533-500) / 16.67 = 33/16.67 = 1.98
-percentile is 97.61(47.61 between 0 and z score saw this on the table)
Parametric v. Nonparametric Tests
parametric tests: inferential statistical test based on assumptions about a population
(making assumptions about distribution)
nonparametric tests: inferential statistical test not based on assumptions about the population
(distribution free tests) ranked ordinal data rather than calculating means
3 key assumptions for the z test
1. Dependent variable is a scale measure or variable
2. Participants have to be randomly selected
3. Population distribution is approximately normal (okay if the sample sizes are 30 or more)
6 Steps of Hypothesis Testing
1. Identify populations, distribution, and assumptions and then choose the appropriate
hypothesis test
2. State the null and research hypothesis in both words and symbolic notation
3. Determine the characteristics of the comparison distribution
4. Determine the critical values, or cutoffs, that indicate the points beyond which we will reject
the null hypothesis **most important step**
5. Calculate the test statistic
6. Decide whether to reject or fail to reject the null hypothesis
The z Test
-when we know the population mean and the standard deviation
-the z test:
Do Questions in Textbook chapter 7